Recently, a plurality of users remotely control a single camera unit over a network and receive shot images via the network, thanks to widespread use of the Internet. A problem involved is that the plurality of users are dispersed and each of them operates the common camera unit without knowing the circumstances of the other users; simultaneous attempts to use the same camera unit have naturally resulted in conflicting requests for the use of the camera unit.
Japanese Patent Laid-Open No. 042278/1998 proposes an imaging unit which controls the period for control right in response to a plurality of control requests based on the occurrence of control requests. The imaging unit registers a plurality of clients which issue control right requests in a camera control queue, a type of buffer for registering information on control instruction in chronological order. Detecting that a control request has been issued from one of the plurality of clients registered in the queue, the imaging unit determines whether to switch the control right based on the period for control right assigned to another client in case the source client has no longer its control right. Determining that the control right is to take pace, the imaging unit updates the contents of the camera control queue in order to switch the control rights between clients. In this way, when a single imaging unit is controlled by a plurality of users, a control request from a client is discarded while another client is controlling the imaging unit, based on identification of each client.
The related art technology requests each client to own a client ID; this approach is not suited for a system where a general-purpose browser controls an imaging unit. An alternative approach of using an IP address for identification is not effective either, because an IP address is converted in case data is transmitted across a plurality of networks.
An object of the invention is to avoid confusion of operation despite racing of operation requests when a plurality of users attempt to operate a common camera unit via a network. Another object of the invention is to allow a user to operate the camera unit by using a general-purpose browser from anywhere in a network without experiencing confusion or using a special ID for identifying client terminals.